REASONING GP · Clinical algorithm · Quick reference

Abdominal pain in adults — triage and diagnostic approach

Daytime GP and OOH/111, face-to-face or remote. Exclude the surgical abdomen and the vascular catastrophes, localise by region to a named diagnosis, then decide who leaves by ambulance, by letter, or with a treatment and a review.
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AdultsGP + OOHDiagnosis firstv1.0 · Sep 2026
Core rule. Three questions come before the history: is the abdomen surgical, is the patient shocked, and could she be pregnant? Any woman of reproductive age with abdominal pain has an ectopic pregnancy until a pregnancy test says otherwise. Pain out of proportion to the examination, pain with a pulsatile mass, and pain with hypotension are vascular emergencies. The old, the frail and the immunosuppressed present late and softly.
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Before any history: is this an emergency now? Stop the consultation and call 999 if any of these is present
Shock — systolic BP <90, pulse >120, mottled or clammy · rigid or peritonitic abdomen · sudden severe pain with a pulsatile mass, or back/flank pain with collapse over 50 · severe constant pain with a soft abdomen in AF or vascular disease · haematemesis or melaena with instability · positive pregnancy test with pain, bleeding or shoulder-tip pain · fever with jaundice and rigors · tender irreducible groin or scrotal lump. ABCDE, observations, nil by mouth, exact onset time, hand over. Do not delay transfer for bloods, urine, imaging or analgesia decisions.
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Define the pain in four lines Enough to place the patient in the table below

Time & onset

Instantaneous and maximal at onset (perforation, ruptured AAA, ectopic, torsion) · over hours with migration (appendicitis) · colicky in waves (obstruction, renal or biliary colic) · days to weeks (inflammatory, malignant).

Site & radiation

Epigastric to back (pancreatitis, AAA) · RUQ to scapula (biliary) · loin to groin (renal) · iliac fossa (appendix, diverticulum, ovary, ectopic) · suprapubic (bladder, uterus) · generalised (peritonitis, obstruction, ischaemia).

Context

LMP and contraception in every woman of reproductive age · previous abdominal or pelvic surgery · known AAA, AF, vascular disease · alcohol, gallstones, NSAIDs, steroids, anticoagulants · immunosuppression · diabetes.

Associated

Vomiting, absolute constipation and no flatus · blood per rectum, melaena · fever, rigors, jaundice · dysuria, haematuria · vaginal bleeding · weight loss · thirst and polyuria.
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Red-flag screen: trigger → concern → destination → what to do before handover One row is enough; do not add up reassuring features
Trigger / red flagLeading concern · destinationDo now · do not delay
Sudden severe abdominal, back or flank pain over 50 with collapse, hypotension, a pulsatile expansile mass or unequal femoral pulses; known AAA. First-episode "renal colic" over 50 is an AAA until excluded. Ruptured or symptomatic AAA
999 now		 Say "suspected ruptured AAA" on the handover so the vascular pathway starts from the call. Do not palpate repeatedly, do not arrange an outpatient ultrasound, do not give analgesia and review.
Rigid, board-like or peritonitic abdomen: guarding, rebound, percussion tenderness, lying still; severe epigastric pain to the back with vomiting; pain on NSAIDs, steroids or known ulcer. Perforated viscus · pancreatitis · peritonitis
999 now		 Nil by mouth, observations, drug history on the handover. Analgesia is permitted and does not mask the diagnosis. Do not give a PPI and review.
Severe constant pain with a soft abdomen — pain out of proportion to examination — in AF, heart failure, recent MI, vascular disease or over 65. Acute mesenteric ischaemia
999 now		 State "pain out of proportion, query mesenteric ischaemia" on the handover; it is diagnosed by CT angiography within hours and missed by a normal examination.
Any woman of reproductive age with abdominal or pelvic pain, especially with amenorrhoea, vaginal bleeding, shoulder-tip pain or syncope; IUD, previous ectopic or assisted conception. Ectopic pregnancy · ovarian torsion · PID
999 if unstable Same-day EPU / gynaecology		 Urine pregnancy test in every woman of reproductive age, whatever the contraception (NG126). A positive test with pain is an EPU assessment today, not a routine scan. Sudden severe unilateral pain with vomiting is torsion — same-day gynaecology even if the pain has eased.
Colicky pain with vomiting, distension, absolute constipation and no flatus; previous surgery, hernia, or a tender irreducible groin or scrotal lump. Obstruction · strangulated hernia · volvulus
999 if peritonitic or irreducible hernia Same-day surgical		 Examine both groins and the scrotum — a strangulated femoral hernia is easily missed in an elderly woman. Nil by mouth. No laxative, enema or antiemetic and review.
Fever, rigors, tachycardia or confusion with abdominal pain; right upper quadrant pain with jaundice and fever (Charcot's triad); loin pain with fever and vomiting; immunosuppressed or asplenic. Cholangitis · pyelonephritis · intra-abdominal or neutropenic sepsis
999 if sepsis or jaundice with rigors Same-day acute		 Observations and sepsis assessment (NG51). Jaundice with fever and RUQ pain is an emergency biliary decompression pathway, not an oral antibiotic. Pyelonephritis with vomiting, pregnancy or frailty needs admission.
Haematemesis, coffee-ground vomiting, melaena, or anaemia with epigastric pain; anticoagulants, NSAIDs, alcohol excess or known varices. Upper GI bleed · bleeding ulcer
999 if haematemesis or shock Same-day acute		 Observations including postural BP. Stop NSAIDs; discuss anticoagulation with the receiving team. Do not start a PPI and review after melaena.
Cancer feature with chronic or recurrent pain: abdominal or pelvic mass or ascites, any age · 40+ with weight loss and abdominal pain · 60+ with weight loss plus new diabetes, nausea, back pain or bowel change · 55+ with upper abdominal pain plus weight loss, reflux or dyspepsia · dysphagia any age · jaundice 40+ · women 50+ with new IBS-like symptoms in 12 months. Colorectal · ovarian · pancreatic · upper GI cancer
Urgent suspected-cancer referral or direct-access test within 2 weeks · NICE NG12		 Match the test to the criterion (NG12): FIT ≥10 µg Hb/g → USC referral · CA-125; if ≥35 IU/mL, urgent abdominal and pelvic ultrasound (ultrasound first if ascites or a mass) · urgent direct-access CT at 60+ for pancreatic cancer · urgent direct-access OGD for dysphagia, or 55+ with weight loss plus upper abdominal pain, reflux or dyspepsia · unexplained mass, or jaundice 40+, is a direct USC referral. A normal test with persisting symptoms does not close the question.
Pain without abdominal signs is not benign. Thirst, polyuria and deep sighing breathing = DKA (glucose and ketones now; 999 if ketones ≥3.0 mmol/L). Epigastric pain with sweating over 40 = inferior MI (ECG before any PPI). Also lower-lobe pneumonia, Addisonian crisis, hypercalcaemia.
Safety rule. A soft abdomen, a normal temperature, normal bloods and a settled pain each lower probability; none excludes AAA, ischaemia, ectopic pregnancy or early appendicitis. Analgesia does not mask the surgical abdomen. If a row applies and the safe destination is unavailable, escalate.
Colour is semantic: red = emergency now · amber = same-day acute assessment · blue = define/assess · green = primary-care diagnosis · purple = uncertain / specialist route (including 2WW). Continued on page 2: classification, regional classifier, routine referral, primary-care treatment, endpoint.
REASONING GP · Abdominal pain in adults — triage and diagnostic approach
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Focused examination and investigation Remote assessment that cannot examine the abdomen is an escalation criterion

Measure

Pulse, BP with postural drop, RR, SpO₂, temperature, GCS. Glucose and ketones if diabetic or vomiting. Urine pregnancy test in every woman of reproductive age.

Examine

Distension and scars · gentle palpation for guarding, rebound, percussion tenderness and a pulsatile mass · Murphy's and RIF rebound · both groins and the scrotum, always · rectal examination where melaena or obstruction is in question · pelvic examination where indicated.

Same-day tests

Urine dipstick and MSU (not diagnostic of UTI in women with pelvic pain, or over-65s) · FBC, U&E, CRP, LFT, amylase, glucose · ECG if epigastric pain over 40.

Directed tests (not triage)

FIT, CA-125, coeliac serology, faecal calprotectin, H. pylori testing, ultrasound for gallstones, outpatient OGD or colonoscopy.
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Classify: three exits, not two "Non-specific abdominal pain" is a decision to review, not a diagnosis to discharge on

Surgical or serious cause likely

Any red flag, peritonism, shock, a positive pregnancy test with pain, obstruction or sepsis. Output: name the leading concern; use the destination above; record observations, pregnancy test result, analgesia with dose and time.

Cause established and treatable in primary care

No red flags, normal observations, the whole pain explained by one regional diagnosis below. Output: record the diagnosis, the supporting findings, the treatment started, and the review date.

Unclassified / uncertain

Undifferentiated pain with normal observations, early appendicitis that cannot be excluded, or recurrent pain with a cancer feature. Output: do not default to "constipation", "gastritis" or "IBS" at a first presentation. State the uncertainty, the section-6 route where one applies, and an active review within 12–24 hours.
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Regional classifier Only once the red-flag screen is negative
Right iliac fossaAppendicitis — central pain migrating over 6–24 hours with anorexia, low-grade fever and localised tenderness: same-day surgical assessment, and early appendicitis can have normal bloods. In women, also ectopic, torsion and PID.
Left iliac fossaDiverticulitis — localised tenderness, fever, change in bowel habit over 50: oral antibiotics and review only if systemically well with no peritonism (NG147); unwell, peritonitic or failing at 48 hours is admission. 5–10% of CT-confirmed diverticulitis proves to be malignancy — arrange interval investigation.
Right upper quadrantBiliary colic — post-prandial, 1–6 hours, no fever, Murphy's negative: analgesia, ultrasound, routine surgical referral. Acute cholecystitis — constant pain, fever, positive Murphy's: same-day surgical.
EpigastricDyspepsia, GORD, peptic ulcer — burning, food or NSAID related, no alarm features: test for H. pylori or give a PPI trial (CG184). Always exclude cardiac pain over 40 and pancreatitis. Alarm features, or 55+ with weight loss → section 6 / NG12.
Loin to groinRenal colic — severe colicky pain, restless patient, haematuria: NSAID analgesia and CT KUB within 24 hours (NG118). Fever, a single kidney, pregnancy or obstruction is an emergency. A first episode over 50 is an AAA until excluded.
Suprapubic / pelvicUTI — dysuria, frequency, urgency without pelvic pain in a non-pregnant woman. PID — deep pain, discharge, cervical excitation: treat empirically and refer to sexual health. Retention — palpable bladder: catheterise or admit.
Generalised / functionalConstipation — only with a consistent history and no red flags, never the explanation for vomiting with absolute constipation. Gastroenteritis — diarrhoea and vomiting with an exposure history; pain-predominant illness without diarrhoea is not gastroenteritis. IBS — Rome-type pain with bowel-habit change over at least 6 months, after normal FBC, CRP, coeliac serology and calprotectin (CG61).
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Refer routinely from this consultation Not same-day, not 999 — the cases that leave by letter
Symptomatic gallstones on ultrasound → routine upper GI surgery (CG188). Dyspepsia unresponsive to eradication and a full-dose PPI, no NG12 alarm feature → routine gastroenterology (CG184). Suspected inflammatory bowel disease — raised faecal calprotectin, or diarrhoea with blood, weight loss or nocturnal symptoms → gastroenterology, urgently if unwell. Suspected coeliac disease — positive tTG-IgA with total IgA → gastroenterology for biopsy; do not start a gluten-free diet first (NG20). Chronic pelvic pain or suspected endometriosis → gynaecology, or a specialist service where imaging is negative but symptoms persist (NG73). Recurrent stones, a symptomatic hernia, or constipation failing two agents → the relevant routine clinic. Interval investigation after CT-confirmed diverticulitis. What remains below is what primary care treats today.
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The only treatment decisions that belong in this consultation What primary care treats today
Analgesia while the diagnosis is settledGive it: analgesia does not mask the surgical abdomen. Paracetamol first line; an NSAID for renal or biliary colic (diclofenac 75 mg IM or 100 mg PR, or oral ibuprofen) unless there is bleeding risk, GI ulceration, renal impairment or pregnancy (NG118). Avoid NSAIDs where perforation or GI bleeding is suspected.
Uncomplicated diverticulitis, systemically wellSimple analgesia, clear fluids and review at 48 hours; an oral antibiotic only if systemically unwell, immunosuppressed or with significant comorbidity (NG147). Safety-net: worsening pain, fever, vomiting or peritonism means same-day surgical assessment.
Dyspepsia / suspected peptic ulcer, no alarm featuresStop the NSAID where possible; full-dose PPI for 4 weeks, or test and treat for H. pylori — with a 2-week PPI washout before urea breath or stool antigen testing, or the test is falsely negative (CG184). Review at 4–8 weeks.
Uncomplicated lower UTI, non-pregnant womanNitrofurantoin or trimethoprim per local guidance for 3 days (NG109). Pregnancy, men, catheters, recurrence or systemic features change the pathway — send an MSU. Loin pain, fever or vomiting is pyelonephritis, not cystitis.
Peritonitis, obstruction, AAA, ischaemia, ectopic, sepsis, GI bleedTransfer is the treatment. Nil by mouth. No laxative or enema in obstruction; no PPI in melaena; do not treat a positive dipstick in a woman with pelvic pain and a positive pregnancy test; no outpatient scan for a suspected AAA. Analgesia is permitted if it does not delay conveyance.
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Endpoint and documentation Finish with one of four conclusions and a named owner

1 · Time-critical serious

999 route taken; suspected diagnosis, onset, observations with postural BP, pregnancy test result, abdominal findings, analgesia with dose and time.

2 · Serious possible

Same-day surgical, gynaecological or acute assessment arranged; the question being excluded, who was spoken to, deadline to be seen.

3 · Cause established

Diagnosis and supporting findings; observations and tests; treatment with dose and duration; review date; safety-net understood.

4 · Unclassified

Uncertainty stated; active review booked within 12–24 hours; section-6 referral or NG12 test sent, with date; deterioration criteria and a named owner.
Why a primary-care diagnosis is safe today, in one line: no row on the page-1 screen applies · pulse, BP, temperature and RR normal and recorded · pregnancy test negative in every woman of reproductive age · abdomen soft with no localised peritonism, groins and scrotum examined · the whole pain explained by one regional diagnosis · NG12 criteria considered · written safety-net and a booked review. Safety-net wording: call 999 or go to A&E if the pain becomes severe or constant, the abdomen becomes hard or too painful to touch, you vomit repeatedly, you pass blood or black stools, you faint or become cold and clammy, or you develop a fever with shivering; contact us the same day if the pain moves to one place or worsens over hours.
OOH / remote limitation. Convert to face-to-face or emergency assessment if the abdomen cannot be examined; observations cannot be obtained; a pregnancy test cannot be done in a woman of reproductive age; the pain is severe, migrating or worsening during the call; the patient is over 65, frail, immunosuppressed or anticoagulated; or safe transport and timely review cannot be guaranteed. Under time pressure the default is the safer destination.
Clinical decision support only; follow local emergency-transfer and referral policies and check doses against the current BNF. Source hierarchy: NICE guidelines and CKS first, then BNF/MHRA for doses and safety, then national specialty guidance. Sources: NICE NG12 Suspected cancer (May 2025) · NG147 Diverticular disease · CG184 Gastro-oesophageal reflux disease and dyspepsia · NG118 Renal and ureteric stones · NG109 Urinary tract infection (lower) in women · NG126 Ectopic pregnancy and miscarriage · NG73 Endometriosis · NG20 Coeliac disease · CG61 Irritable bowel syndrome · CG188 Gallstone disease · NG51 Sepsis · NICE CKS Abdominal pain, Dyspepsia, Diverticular disease · BNF · MHRA. Review after any guidance or medicines-safety update, otherwise every 6 months. © Reasoning GP · gpreasoning.uk